Fuel feed and exhaust nozzle control for gas turbine engines



Nov. l, 1960 F, c, MQCK 2,958,186

`FUEL FEED ANO EXHAUST -NOZZLE CONTROL FOR GAS TURBINE' ENGINES 'Original Filed April 2o,4 195o 5 Sheets-Sheet 1 QQ m T l Q m l m S m. MHH E E Ew QI! MY MN NN/ r 1 S l QQ E E E N i, EN mw a. ww D mw n uw ww E E H ELF E .Oil

NOV. 1, 1960 F C, MQCK 2,958,186s

FUEL FEED AND EXHAUST -NozzLE CONTROL FOR GAS TURBINE ENGINES original Filed April 2o, 195o :s sheets-sheet 2 N N N MMM IN V EN TOR.

FFAA/f6. M00/ MNM/f Arrow/fr i Nov. l? 1960 2,958,186

FUEL FEED AND EXHAUST NozzLE CONTROL FOR GAS TURBINE ENGINES F. C. MOCK 3 Sheets-Sheet 5 Original Filed April 20, 1950` NF4@ 4.4.-. NWOAU V8 GEEL-i 13nd 2,958,l6 Patented Nov. 1, 1960 FUEL FEED AND EXHAUST NOZZLE CONTROL FR GAS TURBINE ENGINES Frank C. Mock, South Bend, Ind., assigner to The Bendix Corporation, a corporation of Delaware Continuation of application Ser. No. 156,980, Apr. 20, 1950. This application May 25, 1955, Ser. No. 511,077

24 Claims. (Cl. 60-35.6)

This application is a continuation of my copending application Serial No. 156,980, tiled April 20, 1950 and now abandoned, covering a fuel feed and exhaust nozzle control for gas turbine engines.

rThis invention relates to controls for jet engines, and more particularly to controls of that type wherein the rate o-f -fuel feed is coordinated with the area of the discharge jet or exhaust nozzle, Such controls basically have means for varying the area of the jet, which may take the form of a movable tail cone or a clam-shell exhaust nozzle or jet, and fuel feed mechanism operatively connected thereto. This arrangement renders control of jet powered aircraft more flexible. As one example, it permits engine operation at high speeds with relatively low jet thrust, a condition desirable when a pilot is Vapproaching a landing iield or deck and must be ready for rapid acceleration in the event of a wave-off; as another example, it enables a pilot to raise the burner temperature to the rated value. for maximum power without overspeedin-g the engine when the temperature of the air entering the compressor is low. In the first example, the jet area would be enlarged to increase the drop across the turbine and reduce thrust while. maintaining a fairly high rate of fuel feed, and in the second example, the jet area would be reduced to reduce the drop across the turbine and increase jet thrust while at the same time permitting an increase in the rate. of fuel feed Without producing excessive engine speed.

An object of the instant invention is to provide a control of the coordinated fuel feed and jet area type wherein a pilot, when he desires to accelerate or decelerate, may set his control instantly at the selected power position, whereupon the engine will automatically accelerate or decelerate to the desired speed as rapidly as is consistent with safe burner temperatures, and also avoid blow-out during acceleration or burner die-out during deceleration, with coordinated predetermined scheduling of jet nozzle area or jet thrust.

Another object of the invention is to provide a control for jet engines having automatically operating means for coordinating the rate of fuel feed and jet nozzle area in a manner such as to avoid compressor surge dun'ng acceleration.

Another and more speciiic object of the invention is to provide a control for jet engines wherein both the rate of fuel [feed and the area of the jet are scheduled on the basis of selected parameters during acceleration and/or deceleration as a function of engine speed.

Another object of the invention is to provide a control of the type specified wherein during acceleration the rate of fuel feed will increase at a maximum, but within an upper limit having as its modulus burner temperature and/ or blow-out while at the same time avoiding the surge area, if such be present, and the means for varying the area of the jet will be controlled in coordinated relation with the rate of fuel feed between maximum and minimum area positions in a manner such as to obtain a high degree of engine efficiency.

A further object of the invention is to effectively combine and coordinate in a control for jet engines a manually adjustable throttle valve and associated all-speed governor for controlling the area of a metering restriction, a speed responsive regulator for maintaining a predetermined head across said restriction, and means for varying the area of the exhaust jet.

A still further object of the invention is to generally improve controls of the type specified.

Another object or" this invention is to provide speed governor means for controlling the flow of fuel through valve means during governing operation of the engine, and speed responsive means for modifying the control of fuel ow by the valve means during an acceleration of the engine.

The foregoing and other objects and advantages will become apparent in View of the following description taken in conjunction with the drawings, wherein:

Figure 1 is a View principally in elevation of a jet engine having operatively associated therewith a control embodying the features of the instant invention;

Figure 2 is a schematic view of the control mechanism;

Figure 3 is an enlarged longitudinal section of the positioning or follow-up servo for operating the exhaust jet gate valves; and

Figure -4 is a curve chart illustrating the operation of the improved control.

In Figure l, a turbo-jet engine is shown more or less diagrammatically at 10; it includes a burner system made up of a plurality of annularly disposed combustion chambers, one of which is indicated at 11. An air adapter or header section 12 is detachably connected to the front end of the burner assembly and dire-cts air under pressure to the combustion chambers 11, where it mixes with the fuel discharged from burner nozzles 13, there being one for each combustion chamber. The gases, comprised of expanded air and products of combustion, are discharged from the combustion chambers through stator blades 14 and then through the rotating blades 15 of a turbine 15. A dynamic compressor, not shown, but which may be of the centrifugal type or axial flow type, is driven from the turbine.

Beyond the turbine is a diffuser cone section 16 and a tailpipe section 16', the latter at its outlet terminating in a reaction jet or exhaust nozzle 17, the area of which is adjustable or variable by means of a pair of gate valves 18 and 18', which are mounted on suitable bearings such as trunnions or short shaftsY 19. Also secured on the shafts or trunnions 19 are intermeshing segmental gears 2l) and 21. An arm 22 is provided on one end on lthe upper gear 20 and is connected through the medium of a link rod 23 and a coupling member 24 with a slidable servo motor rod 25, the latter forming part of a positioning or follow-up servo assembly generally indicated at 26 and shown in enlarged longitudinal section in Figure 3.

The servo motor 26 is adapted to operate the gate valves 13 and 18. It comprises an outer cylinder 26 having at its right-hand end a cap 27 formed with a central boss 27 slidably receiving and guiding the rod 25. The inner end of the rod 25 has secured thereon a spring retainer 28, against which the one end of a spring 29 abuts, said spring normally urging the rod 25 in a direction tending to open the gate valves 18 and 18. Within the cylinder 26 is a slidable piston 30, provided with drain ports, two of which are indicated at 31 and 32, and an end chamber 33. Slidably mounted in the piston 30 is a servo pilot valve 34, provided with high pressure inlet ports 35 and a communicating longitudinal bore or passage 36, through which hydraulic pressure Huid may ow to the chamber 33 of the outer piston 30. The Servo valve 34 is also formed with drain ports 37, through which drain fluid may flow to an annular chamber 38, and thence out through the ports 31 and 32 into annular drain chamber 39. From the latter chamber, the drain fluid may ow by way of port 40 and passages 41, 42 and valve port 43 to drain passage 44, which leads to a low pressure source, here shown as fuel inlet conduit 51 (P0 pressure),

see Figure 2.

Hydraulic uid, which in the present instance is fuel under pressure, is supplied to end chamber 45 in the outer cylinder 26 by way of passage 46 having a restricted inlet port 47, Figure 2, which is controlled as a function of engine speed in a manner to be described. The drain passage 42 is preferably vented to end chamber 4S at the inner or right-hand end of piston 30 to insure free movement of the latter.

When the servo pilot valve 34 is moved inwardly or towards the right in a manner to be described, drain annulus or chamber 38 is moved to a predetermined position within the outer servo piston 30. If now hydraulic fluid under pressure (here pump discharge or P1 pressure) is admitted to chamber 45, the piston 30 will move towards the right or in a direction tending -to close the tail gates 18 and 18', until the drain ports 31, 32 register with the annulus 38, whereupon the actuating pressure in chamber 45 Will be reduced and the servo piston 30 will come to rest. The strength of the spring 29 is such .as to open the tail gates 1S and 18 when the servo input and drain pressures become substantially equalized.

Referring now to the fuel control device shown schematically in Figure 2, this comprises a suitable housing or casing generally indicated at 50. An engine-driven fuel pump 52 is mounted in said conduit and draws fuel from a suitable source of supply such as a fuel tank, not shown, by way of conduit 51 and delivers it under pressure 4to chamber or passage 53. A relief or by-pass valve 54 vcontrols a by-pass port 55 and channel 56, leading back to the inlet or low pressure side of the pump 52, said valve being carried by a diaphragm 57, backed by a spring 58, normally urging the by-pass valve 54 to seated position. The spring 58 is mounted in a charnber 59, which is vented to metered fuel or discharge (P4) pressure by means of conduit 60. The effective area of the diaphragm 57 is preferably substantially equal to that of the valve 54, hence the fuel supply or P1 pressure in chamber or passage 53 will be maintained at a constant value above metered fuel or P4 pressure as determined by the strength of the spring 58.

Fuel from the chamber 53 ilows by way of valve port 61 into unmetered fuel chamber 62, thence by Way of conduit 63 through metering orifice or restriction 64 to metered fuel chamber 65, and thence by way of conduits 66 and 67 to fuel manifold 68, see Figure 1, from which it is fed by way of the individual fuel lines 69 to the burner nozzles 13.

Reverting to Figure 2, the port 61 is controlled by a regulator valve 70 of the poppet Itype having a stem 70 connected lto diaphragms 71 and 72, which form movable walls between chambers 62, 73 and 74.

The area of the metering orifice or restriction 61 is regulated by a governor or throttle valve 75, controlled in a manner to be described.

A passage 76 leads from chamber 73 to an impeller chamber 77, the latter communicating with the chamber 74 by way of passage 78, variable oriiice 79 and passage or port 80. A centrifugal impeller 81 is mounted on a shaft 82 having a suitable drive connection with the turbine and compressor, or the engine, in any suitable manner, not shown. Since the impeller 81 is driven in direct relation to turbine and compressor or engine speed, at a fixed area of orifice 79, it will produce a pressure differential between chamber '73 and chambers 62, 74, or across the diaphragms '71 and '72, proportional to the .square of engine speed, subject to modilication for changes in the pressure and/or temperature of the air flowing to the engine in a manner to be described. (The word eng-ine as used herein means the power plant as a whole including the turbine and compressor.) A passage 83 having a restriction 84 therein communicates chamber 74 with the metered fuel chamber 65.

The diaphragms 71 and 72 are shown as being of substantially equal effective area, and a spring 85 backed by an adjustable screw 86 serves as a means whereby the effective differential pressure across the metering orifice 64 may tbe held within certain limits at low fuel ows, as at low idling speeds of the engine. This spring represents a constant, the value of which may vary in accordance with the idling or low speed fuel requirements of different types of engines; its effect becomes negligible and fades out at fuel ows above idling.

The fuel head or metering differential may be corrected for changes in altitude or air density by means of a capsule 87 -responsive to changes in pressure and ternperature and located at a point where it will be exposed to the air iiowing to the engine, or to rampressure. A needle 88 isrconnected to the movable end of the capsule 87 and projects into the orifice '79; its function is to vary the effective area of the latter and thus vary lthe elective differential across the diaphragms 71 and 72 with changes in pressure and/or temperature of the air ilowing to the engine.

Secured on the outer end 0f the shaft 82 is a bracket 90 forming part of an all-speed governor assembly generally indicated at 91, including a pair of centrifugal weights 91', having arms engaging in an annular groove formed on the inner headed end of a sleeve 92, mounted on a reduced extension of the shaft 82. A lever 93 is pivotally supported or fulcrumed at 94. At its one end, the said lever is provided with a bearing fork 95 engaging in an annular recess provided in the outer end of the throttle valve 75, and at its opposite end the said lever 93 is provided with another bearing fork 96 engaging in a similar recess provided -in the outer end of the sleeve 92. A governor spring is indicated at 97; it is seated at its inner end on the governor sleeve 92 and at its outer end is engaged by the one arm of a bell crank lever 98, the other arm of which is pivotally connected to a llink rod 99.

A power control lever is indicated at 1Gb; it is associated with a suitable quadrant 101 and -is secured on a shaft 102 to impart rotation to the latter. rIhe shaft 102 has secured thereon a pair of cams 1&3 and 104. The cam y103 is the tail gate servo cam; as shown, it is -adapted to imp-art movement to a lever 105 which, at its lower end, is pivotally connected to a link rod 106, in

turn connected to the outer end of the servo valve 34 by means of a liexible or universal coupling 107, note Figure 3. The rod 106 projects through a bushing 108 and a suitable seal or packing gland 109. To avoid looseness and play, a spring 110 normally urges the free end of the lever 105 against the active surface of the cam 103, see Figures l and 2.

The cam `104 is adapted to act on the free end of a lever 111, which at its upper end is pivotally connected to the link rod `99.

It wil-l be seen that when the pilots control lever 100 is moved in a power increasing direction (towards the right or clockwise, as shown in the drawings), it will rotate the cams 103 and 104 .in a clockwise direction, whereupon the yrod 106 lwill move the servo valve 34 inward-ly or towards the right, and the cam 104 will act through the link rod 99 and bell crank 98 to compress the `governor spring 97. To facilitate a description of the operation of the invention, graduated positions of the lever 100 are indicated by suitable reference characters which correspond to similar indicia on the curve chart of Figure 4.

An auxiliary acceleration or compressor surge control device is operatively associated with the all-speed governor 91 and its coacting throttle valve 75. In the form shown, it comprises a pair of oppositely extending arms ebenso .l 112, 112 pivotally or rotatably mounted on a shaft 113. 'Ihe arm 112 is provided with a contact 114 adapted to engage a collar or other suitable member 115 secured to or formed on the throttle valve 75. The arm 112 is also provided with a contact member 116 adapted to engage a boss 117 formed on a piston 117', slidable in a cylinder 118, formed with a stop flange `118 and normally urged outwardly by a spring 119, adjustable by means of an exteriorly accessible screw 120. The cylinder 118 is adjustably threaded in the housing 50 of the fuell control device. A diaphragm 121 for-ms a movable wall between chambers 122 and 65, said `diaphragm being connected to the outer end of the arm 112 by means of a link 123. The chamber 122 is vented to the passage 7S and hence to the discharge side (P3 pressure) of the impcller S1 by means of passage 122. A light spring 124 backs up the diaphragm 121 to take out play or slack in the linkage. The differential across the diaphragm 121 is proportional to the square of engine speed, and since this differential is uncompensated for changes in pressure and/or temperature of lthe air flowing to the engine, the various positions assumed by the contacts 114 and 116 will be the same at predetermined engine speeds at all altitudes. Likewise, the various` positions assumed by the governor valve 75 for given or selected engine speeds will be substantially the same at all altitudes, since the pressure and temperature correction is applied to the fuel metering head across orifice 64 in.- stead of to the area of the latter. Hence, the desired point on a fuel feed vs. engine speed curve at which the device becomes effective to modify the rate of fuel feed may be predetermined, assuming a given location of the boss 117 and/or collar 1115. The 4force of the spring 119 should be coordinated with that applied by the governor spring 97 in a manner such that when the governor 911 is reset to accelerate to a high or maximum speed, the governor valve 4will be arrested in its opening movement untill the combined forces exerted by the differential across the diaphragm 121 and the governor spring become sufficient to overcome the resistance interposed by the said spring 119.

As heretofore noted, hydraulic fluid under pressure ows to the chamber 45 of the servo motor 26 by way of conduit 46 and port 47 therein. This port is controlled by a needle 125, which is connected to a diaphragm 126, located in a housing 127 and forms a movable wall between chambers 128 and 129 in said housing. The said diaphragm is backed by a substantially constant rate spring 130 adjustable by screw 131. The chamber 128 is vented to the passage 78 (P3 pressure) by Way of passages 122 and 132, while the chamber 129 is vented to the chamber 65 (P4 or metered fuel pressure) by way of passage 133. The differential across the diaphragm 126 is, therefore, proportional to the square of engine speed `and hence .the travel of the needle becomes a function of engine speed subject to modification by adjustment of spring 130.

An overtemperature cut-off on the jet nozzle area is provided. In the form shown, it comprises a needle 134, Figure 3, `adapted to control the port 43 in the drain channel or passage 42 heretofore described, said needle being connected at its outer end to a lever 135, which is pivotally `anchored at 136 and at its lower end is connected by means `of a link rod 137 (see Figure 1) to the motor driven arm 138 of an actuator 139, and which may be a reversible electric motor or other suitable electrically controlled device. A temperature sensing element in the `form of Va thermocouple 140 is projected into the tail cone section 16 of the engine and is connected at its outer end to a junction box 141, the latter being electrically connected by means of wires 142 and 143 with a converter and amplifier unit 144. Any suitable temperature sensing mechanism available in the open market may be utilized, that here shown being simply for the purposes of illustration.

A low speed or idle stop is indicated at 145 in Fgure 2; it is located for contact by an adjustable member shown in the form of a screw 145' carried by the one arm of lever 93.

Operation The engine may be started and brought up to a selfsustaining speed in any suitable manner, as by an electric starting motor, not shown, having a driving connection with the turbine and compressor, and coacting ignition means. The metering unit 50 would ordinarily be filled with fuel, but assuming it to be empty, the differential across diaphragms 71 and 72 would be substantially zero and valve 70 would be open under the influence of spring 85. When the fuel pump 52 starts, chambers 62, 73 and 74 fill in successive order and `fuel also flows through conduits 66, 67 to the manifold ring 68 and thence through the individual fuel lines 69 to the burner nozzles 13.

The centrifugal pump 81 operates at a fixed ratio of speed with respect to the speed of the turbine and compressor, and for a given area of the metering restriction 64 and the altitude or density control orifice 79, it will produce a pressure differential across the diaphragms 71 and 72 proportional to the square of engine speed. Assuming the diaphragms 71 and 72 to be of equal effective area, the pressure in chamber 73 will be balanced out and any change in pressure in chamber 74 or chamber 62 will correspondingly vary the differential across diaphragms 71 and 72. When the area of the metering orifice 64 is increased to accelerate the engine, the pressure in chamber 62 and passage 63 is momentarily reduced, the differential across diaphragm 71 decreases, and the regulator valve moves toward open position until at a fixed area o-f said orifice and a given engine speed, the regulator is in balance; a decrease in the area of said restriction having the opposite effect.

The pressure differential across diaphragms 71 and 72 is imposed across the metering restriction 64, and since this differential is substantially proportional to the square of engine speed for any given position of the governor valve 75 and aneroid needle 88, the velocity and hence the rate of fuel flow through said restriction will be proportional to the square root of this differential or to the speed directly. To accelerate the engine, and power control lever is moved in a direction to compress the governor spring 97. This resets the all-speed governor 91 and opens the governor or throttle valve 75. The engine now speeds up to a point where the force of the rotating governor weights balances the new setting of the governor spring, whereupon the governor or throttle valve 75 closes to its equilibrium position. During this period of acceleration, the metering head or differential and hence the rate of fuel feed will increase substantially in relation to engine speed, as will also the quantity of air delivered to the burners.

Upon a decrease in the density of the air flowing to the engine, less fuel is required to drive the turbine and compressor at a given speed, and unless this is corrected, the ratio of air to fuel Aduring acceleration at altitude will become so rich as to produce dangerously high burner temperatures. A decrease in density, as by reduction in pressure and/or an increase in temper-rature, causes elongation of bellows 54 and reduction in the area or orifice 79. This correspondingly reduces the pressure in chamber, assuming a given engine speed and a given area of the metering restriction 64, whereupon the regulator valve '70 will tend to close, the metering differential will be correspondingly reduced, and less fuel will be supplied to the burners; an increase in density, as by an increase in pressure and/ or a decrease in temperature, having the opposite effect.

Referring now to Figure 4, it will be noted that the curve chart plots fuel flow against engine speed. The solid lines at 146, 147, 148 and 149 in this figure, which terminate in a diagrammatic representation of jet nozzles at different areas, indicate the quantity of fuel required to run the engine at a steady speed at each particular jet area. In the example illustrated, the area of the jet does not begin to reduce upon acceleration until the control lever 100 is approximately at its intermediate position; note that the area remains unchanged at position M, although there is a progressive increase in the rate lof fuel feed at A, B, C and D. As the throttle lever is moved to positions E, F and G, provided the engine speed is up to where the diierential across the diaphragm 126 can overcome spring 130, the servo piston 30 begins to close the gate valves 18, 18', giving the respective jet areas at N, O, and P. At lower engine speeds where valve 125 is seated, opening the throttle leaves the tail gate area as shown at M.

At any given point of steady speed operation, as at A, B, C, D, E, F, G on curves 146, 147, 148 and 149, engine speed is determined by the all-speed governor setting through lever 100, cam 104 and spring 97, while the tail gate area is determined by cam 103 which is also set by said lever. These cams 103 and 104 are mutually selected or contoured to give the desired operating range.

In general, the active or rise portion of cam 104 will be in the first or lower speed half of the travel of lever 100, while the rise portion of cam 103 will be in the high speed half of travel of lever 100. Expressed in another way, the rst half of the lever travel will result in an engine speed increase from idle to nearly maximum, while the second half of lever travel will chiefly affect the tail gate valve setting with engine speed nearly or at maximum.

On acceleration, however, compression of the governor spring 97 tends to open valve 75 to its limit (until go-verning speed has been reached and governor valve cutolf begins) whereupon the rate of fuel feed is determined by the area of the metering restriction 64 and the fuel metering head across said orifice, as heretofore explained.

Certain engines have a compressor surge characteristic, note the shaded area in Figure 4, which renders it necessary to restrict the acceleration fuel feed at the lower engine speeds as this area is approached and then increases it at higher speeds beyond the surge region, in order to avoid surge and yet attain maximum power and thrust.

In order to enable the engine to accelerate, the tail cone or jet area characteristic line of fuel required vs.

engine speed (for instance the line 146 which is based on area M, Figure 4) must be below the acceleration line (for instance the line at 151), and such regulation is an important feature of the present invention.

At the starting and idling positions of lever 100, the tail gate valves 18, 1S are fully open to the area M. Assuming now that the power control lever 100 is rotated in a direction to accelerate the engine, the cam 103 rotates in a clockwise direction, and the servo pilot valve 34 is pushed inwardly or towards the right. However, at the lower speeds the needle valve 125 will be seated or substantially so, and hence piston 30 will remain inactive and no movement will be transmitted to the gate valves 1S, 18'. As the engine speed picks up, the differential across the diaphragm 126 increases to a point Where it retracts needle 125, whereupon the pressure in servo chamber 45 increases and the servo piston 30 moves inwardly or towards the right, causing the gate valves 18- and 18 to move from an open towards closed position against the resistance of the spring 29; (by closed position is meant a jet area which gives maximum thrust for that particular engine at maximum permissible burner temperature). Thus, as the engine speed passes a contain point, the area of the exhaust jet beings to decrease. By way of example, let it be assumed that the pilot resets the power control lever 100 from a low speed or idle position at B, Figure 4, to a high or maximum speed position at G, then he would simultaneously reset the all-speed governor spring 97 and the tail gate servo valve 34, and the governor or throttle valve would immediately open to the limit set by stops 115, 114, 116, 117, but the area of the exhaust jet would remain unchanged. Due to the fact that the dotted line 151, indicating the rate of fuel feed for acceleration, lies above the line 146 indicating the rate of fuel feed required to -run with the jet area M, the engine can accelerate. The substantially vertical line at 150 indicates the small sharp increase in acceleration fuel due to the sudden increase or quick opening of the metering restriction 64. At the junction of ,this line with line 151, the metering head established by the centrifugal impeller 81 takes effect, and the rate of fuel feed gradually increases, such rate of increase being predicated on the characteristics of the particular engine involved. VIt may have as its parameter or parameters turbine inlet temperature, burner blow-out and/or compressor surge. At a certain predetermined speed, the differential across diaphragm 121 overcomes spring 119, stop 114 is retracted, and the fuel feed increases along line 152 to line 152. Preferably, the adjustment on diaphragm 126 is such that the needle valve 125 will open at a slightly higher speed (note the example illustrated in Figure 4), whereupon the gate valves 18, 118 close to substantially the area at P. The rate of fuel feed now continues to increase along the line 152, 152 to point 153, at which time the centrifugal force generated by the governor weights substantially balances the opposed force of the governor spring 97 with a slight override, and the rate of fuel feed drops down to point G.

To decelerate, the power control lever is moved to the left, or in a counterclockwise direction. This rotates the cams 104 and 103 counterclockwise, decreasing the force exerted by the governor spring 97 and repositioning the servo valve 34 to the left. The engine speed now begins to decrease due to the action of the governor weights 91' tending to close the throttle valve 75, and at the same time the spring 29 pulls the rod 23 to the left and begins to open the gate valves 1S and 18', until the hydraulic drain ports 37 are closed and the pressure in chamber 45 overcomes the force of the spring 29. The dot and dash line at 154 is an attempt to illustrate the deceleration rate when the pilot throttles back from maximum speed at G to idle at A with contact engaging stop 145.

Should at any time during acceleration the tailpipe ternperature exceed a predetermined value, the needle 134 will move inwardly and restrict the drain port 43. This tends to equalize the pressure on the opposite sides of the servo piston 30, preventing further movement of the rod 23 in a direction tending to close the gate valves 18, 18'` until the temperature lowers to a safe value.

The short dotted lines intersecting the steady speed fuel governing positions A-G indicate possible range of governor action in maintaining a rate of fuel feed consistent with exhaust jet area.

To conserve space and simplify the description, the invention has been illustrated in its simplest form schematically. However, those skilled in the art can readily adapt the improved control to engines having different characteristics, in view of the present disclosure. Furthermore, although only one embodiment of the invention has been illustrated and described, various changes in form and relative arrangement of parts may be made to suit requirements.

I claim:

l. In a fuel feed and power control system for a gas turbine engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel conduit for supplying fuel to said burner having a meter restriction therein, a valve for varying the area of said restriction to control the rate of fuel feed, an engine speed governor operatively connected to said valve, means responsive to an engine operating condition related to power output operatively connected to said fuel conduit for reguganarse latng the fuel head across said restriction, means responsive to an engine operating condition related to power output operatively connected to said valve for limiting the fuel ow to the burner during an accelerationof the engine so as to avoid compressor instability, and means responsive to an engine operating condition related to power output operatively connected to said jet area varying means, said last named means being automatically operative to coordinate the effective area of said exhaust jet with the last named engine operating condition which is related to power output.

2. In a fuel feed and power control system for a turbojet engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel conduit for supplying fuel to said burner having a metering restriction therein, a valve for varying the area of said restriction to control the rate of fuel feed, an engine speed governor operatively connected to said valve for controlling the operation of said valve, means responsive to engine speed operatively connected to said fuel conduit for regulating the fuel head across said restriction, and means responsive to engine speed operatively connected to said jet varying means, said last named means being operative as a function of engine speed to coordinate the effective area of said exhaust jet with engine speed.

3. In a fuel feed and power control system for a gas turbine engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including engine speed governor means for varying the rate of fuel feed to the burner, means for resetting said governor to select an operating speed for the engine, means for actuating said jet varying means, means operatively connected to said actuating means for causin-g a reduction in the area of the exhaust jet to lag an increase in the rate of fuel feed when the engine is accelerated, said last named means being responsive to an engine operating condition related to power output and rendering said actuating means effective to reduce the area of said exhaust jet during an acceleration of the engine, and means responsive to changes in an engine operating temperature for modifying the operation of said actuating means.

4. In a fuel feed and power control system for a turbojet engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel conduit for supplying fuel to said burner having a metering restriction therein, a valve for varying the area of said restriction to control the rate of fuel feed, an all-speed governor operatively connected yto said valve, means for regulating the fuel head across said restriction automatically operative as a function of engine speed to maintain the rate of fuel feed within predetermined limits irrespective of how suddenly said valve may be opened to accelerate the engine, a control member movable to different positions to reset said governor and valve and thereby select an operating speed for the engine, and a positioning servo motor for actuating said jet varying means including a control element adapted to be reset by said control member.

5. A control system as claimed in claim 4 wherein said positioning servo-motor also includes a follow-up device responsive to changes in an engine condition related to power output.

6. A control system as claimed in claim 4 wherein said servo motor is of the hydraulic type having a control element in the form of a pilot valve which is operatively connected to said control member and said follow-up device consists of a hydraulic piston provided with control means responsive to changes in engine speed and adjustable to predetermine the phase relationship of the rate of fuel feed and change in jet nozzle area.

7. In a fuel feed and power control system for a turbojet engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including a fuel control element for varying the rate ofVK fuel feedh to the burner and means for regulating the fuel pressure drop across said element, a positioning f servo motor including a movable control valve means and a follow-up piston member for `actuating said jet varying means,.and a power control member operatively connected to said fuel control element and said movable control valve means for preselecting an engine operating speed and forpreselecting the degree of actuation of said jet varying means.

8. In a fuel feed and power control system for a turbojet engine having a` compressor, a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including an element for varying the rate of fuel. feed, means for actuating said jet varying means, means responsive to an engine operating condition which 'is related to power output associated with said actuating means for causing a reduction in the area of the exhaust jet to lag 'ani increase in the rate of fuel feed during an acceleration of the engine, and means operatively connected to said element for modifying the rate of fuel feed as a function of engine speed to avoid compressor instability during an acceleration of the engine.

, 9. In a fuel feed and power control system for a turbojet engine having a compressor, a burner, an exhaust jet and means' for varying the effective area of said jet, a fuelmetering device including an element for varying the rate of fuel feed, a power control member resettable to different positions to select an operating speed for the engine, a servo motor including a control member resettable in coordinated relation to the selected speed and a follow-up memberadapted to operate the jet varying means following a resetting of said control member, means operatively connected to said element for retarding. the rateY of fuel feed to avoid compressor instability when said power control member is reset to accelerate the engine, and means responsive to an increase in engine speed operatively connected to said last named means for overcoming the action of said retarding means and for rendering said follow-up member effective to reduce the area of the exhaust jet.

l0. In a fuel feed and power control system for a turbojet engine having a compressor, a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including a throttle valve for varying the rate of fuel feed and an engine speed governor operatively connected to said valve, a power control member operatively connected to said governor and valve and resettable to different positions to select an operating speed for the engine, means engageable with said throttle valve to retard opening movement of the latter to avoid compresser instability when said governor and valve are reset to accelerate the engine, a servo motor for actuating said jet varying means comprising a control member positionable Vas a function of the position of said power control member and a follow-up member for operating the jet varying means following a change in engine speed, and means responsive to changes in engine speed for modifying the action of said retarding means.

ll. In a fuel feed and power control system for a turbojet engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including a valve for varying the rate of fuel feed, an all-speed governor operatively connected to said valve, a power control member for resetting said governor to select an operating speed for the engine, means for actuating said jet varying means, means operatively connecting said power control and said actuating means whereby when the engine is accelerated a reduction in the area of the exhaust jet is caused to lag an increase in the rate of fuel feed, means responsive to an engine operating condition for automatically rendering said actuating means effective to reduce the area of said exhaust jet following an increase in engine speed, and means responsive to changes in a temperature indicative of turbine temperature operatively connected to said actuating means for modifying the operation of said actuating means to prevent closing of the jet varying means under conditions of excessive turbine temperatures.

12. A control system as claimed in claim l1 -wherein said actuating means comprises a servo-motor means having a control member which is settable Vin relation to a preselected engine speed and a follow-up device which is energized subsequent to a setting of said control member to effect actuation of said jet varying means.

13. In a fuel feed and power control system for a gas turbine engine having a burner, an exhaust jet and means for varying the eective area of said jet, a fuel conduit for supplying fuel to the burner having a metering restriction therein, engine speed governor means for controlling said metering restriction such that the flow of fuel therethrough varies inversely with engine speed, means operatively connected to said conduit for regulating the fuel head across said restriction, means operative to coordinate the eective area of said exhaust jet with an engine operating condition which is related to power output, said last named means including fluid pressure actuated means responsive to a control uid pressure, control means responsive to said engine operating condition related to power output for regulating said control uid pressure and other means responsive to an engine temperature operatively connected to said co-ordinating means for modifying said control fluid pressure to limit the minimum effective area of said exhaust jet as a function of said engine temperature.

14. A control system as claimed in claim 13 wherein said other meansl responds to tailpipe temperature and is adapted to override control of said exhaust jet area by said coordinating means whenever said temperature exceeds a predetermined value.

15. In a fuel feed system for an engine the combination of engine speed governor means including a valve member for controlling fuel flow to the engine as an inverse function of engine speed, means for controlling said governor means to select an engine operating speed, engine speed responsive means separate from said governor means, resilient means connected to oppose said engine speed responsive means, and a mechanism connecting said engine speed responsive means to said governor means and said resilient means, said resilient means being operable to limit movement of'said governor means in a fuel ow increasing direction following a request for an acceleration to a selected engine operating speed, said speed responsive means being operable to overcome said resilient means and thereby modify the operating position of said governor means as a function of engine speed during an acceleration of the engine whereupon the fuel flow to the engine is maintained below a predetermined limiting valve to avoid compressor instability.

16. A fuel feeding system as claimed in claim l5 wherein said speed governor means includes a fuel ow controlling valve means, and wherein said mechanism is operatively connected to said valve means and arranged to control the position of said valve means during an acceleration of the engine, said mechanism being operable to permit fuel enriching movement of said valve means at a predetermined engine speed.

17. vA fuel feeding system as claimed in claim 15 plus additional engine speed responsive means for regulating a fuel pressure head across said valve member as a function of engine speed.

18. A fuel feeding system for an engine comprising a conduit for conducting fuel flow to the engine, valve means operatively connected to said conduit for controlling fuel flow therethrough, engine speed responsive governor means for controlling the operation of said valve means and thus fuel flow through said conduit as an inverse function of engine speed, means operatively connected to said conduit for regulating the fuel pressure drop across said valve means as a function of engine speed, means responsive to engine speed and valve stop means operatively connected to said speed responsive means and said valve means, said valve stop means being actuated in response to a predetermined engine speed during an acceleration of the engine to cause an increase in the maximum flow area controlled by said valve means.

19. A fuel feeding system for a gas turbine engine having a burner and a compressor, a conduit for conducting fuel to the burner, a flow restriction in said conduit, valve means controlling said restriction, engine speed responsive Vgovernor means for controlling said valve means', and engine speed responsive stop means operatively connected to said valve means for limiting the maximum area of said restriction to a fixed value during an acceleration of the engine below a predetermined speed said stop means being rendered inoperative at said predetermined speed to permit said valve means to move in an opening direction and cause a corresponding increase in fuel iiow to said burner.

20. A control system as claimed in claim 19 wherein means responsive to engine speed is provided for controlling a fuel pressure drop across said restriction to vary as a function of engine speed.

2l. A control system as claimed in claim 19 wherein said engine speed responsive stop means responds to a predetermined engine speed to permit an opening movement of said valve means with respect to said restriction, whereby the fuel flow to the burner is enriched to increase the rate of engine acceleration above said predetermined speed.

22. In a control system for a turbo-jet engine, a power control lever, a throttle valve for controlling fuel flow to the engine, an engine speed governor connected to said valve, means for varying the effective area of the exhaust jet, power means for actuating said jet varying means, means operatively connected to said power control lever, said power means and said engine speed governor whereby the engine operating speed of said engine and the degree of actuation of said jet varying means are coordinately controlled as a function of the position of said power control member, means for regulating the fuel metering head across said throttle valve, first means responsive to an engine operating condition which is related to power output for rendering said power means effective to initiate a change in the area of the exhaust jet, and second means responsive to an engine operating condition which is related to power output for opposing full -opening movement of said throttle valve for avoiding compressor instability when the rate of fuel feed is increased to accelerate the engine.

23. In a fuel feed and power control system for a turbojet engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including a valve for varying the rate of fuel feed to the burner, an all speed governor operatively connected to said valve, a power control member for resetting said governor to select an operating speed for the engine, means for actuating said jet varying means including a source of fluid pressure, pressure responsive means responsive to said fiuid pressure operatively connected to said jet varying means for operating the same, valve means for controlling said iiuid pressure, linkage means operatively connected to said power control member and said valve means, means operative with said valve means to cause a reduction in the area of the exhaust jet to lag an increase in the rate of fuel feed during an acceleration of the engine, means responsive to engine speed operatively connected to said last named means and operative to automatically render said valve means operative to reduce the area of said exhaust jet following an increase in engine speed, and means responsive to changes' in turbine temperature operatively connected to said valve means for modifying the operation of said valve means to prevent closing of the jet varying means under a condition of excessive turbine temperature.

24. In a fuel feed and power control system for a turbojet engine having a burner, an exhaust jet and means for varying the effective area of said jet, a fuel metering device including a valve for varying the rate of fuel feed to the burner, an all speed governor operatively connected to said valve, a power control member for resetting said governor to select an operating speed for the engine, means for actuating said jet varying means including a source of fluid pressure, pressure responsive means responsive to said lluid pressure operatively connected to said jet varying means for operating the same, valve means for controlling said fluid pressure, a cam member operatively connected to and actuated by said power control member, a lever member actuated by said cam member operatively connected to said valve means for actu- 14 ating the same to thereby control said uid pressure as a function of the position of said power control member, means responsive to engine speed for inducing a lag in the response of said fluid pressure to changes in the position of said power control member during an acceleration of the engine.

References Cited in the le of this patent UNITED STATES PATENTS 2,457,595 Orr Dec. 28, 1948 2,688,841 Decher et al Sept. 24, 1954 2,706,383 Jacobson Apr. 19, 1955 2,786,331 Williams Mar. 26, 1957 UNITED STATES PATENT OFFICE CERTIFICATION OE CORRECTION Patent No, 2,958,186 November l, 1960 Frank C. Mock It is hereby certfedthat error appears n the above numbered paten't requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 58, for "6l" read 64 column 6, lines 65 and 66, after "chamber"1 insert 74 Signed and sealed this 4th day of July I96I (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

